SEXUAL SELECTION 101 



If the numbers be wholly kept down by the causes just indi- 

 cated, as will often have been the case, natural selection will 

 be powerless in certain beneficial directions; but this is no 

 valid objection to its efficiency at other times and in other 

 ways; for we are far from having any reason to suppose that 

 many species ever undergo modification and improvement at 

 the same time in the same area. 



SEXUAL SELECTION. 



Inasmuch as peculiarities often appear under domestica- 

 tion in one sex and become hereditarily attached to that sex, 

 so no doubt it will be under nature. Thus it is rendered pos- 

 sible for the two sexes to be modified through natural selec- 

 tion in relation to different habits of life, as is sometimes the 

 case ; or for one sex to be modified in relation to the other 

 sex, as commonly occurs. This leads me to say a few words 

 on what I have called Sexual Selection. This form of selec- 

 tion depends, not on a struggle for existence in relation to 

 other organic beings or to external conditions, but on a 

 struggle between the individuals of one sex, generally the 

 males, for the possession of the other sex. The result is not 

 death to the unsuccessful competitor, but few or no offspring. 

 Sexual selection is, therefore, less rigorous than natural se- 

 lection. Generally, the most vigorous males, those which are 

 best fitted for their places in nature, will leave most progeny. 

 But in many cases, victory depends not so much on general 

 vigour, as on having special weapons, confined to the male 

 sex. A hornless stag or spurless cock would have a poor 

 chance of leaving numerous offspring. Sexual selection, by 

 always allowing the victor to breed, might surely give in- 

 domitable courage, length to the spur, and strength to the 

 wing to strike in the spurred leg, in nearly the same manner 

 as does the brutal cockfighter by the careful selection of his 

 best cocks. How low in the scale of nature the law of battle 

 descends, I know not ; male alligators have been described as 

 fighting, bellowing, and whirling round, like Indians in a 

 war-dance, for the possession of the females: male salmons 

 have been observed fighting all day long; male stag-beetles 

 sometimes bear wounds from the huge mandibles of other 



